Theoretical study on the mechanism of CO2 adsorption and reduction by single-atom M (M = Cu, Co, Ni) doping C2N

The capture and further conversion of carbon dioxide into useful fuels and value-added chemicals is critical to addressing the growing problem of global warming and promoting sustainable human development. In this work, the adsorption and activation of CO2 on the surface of single-atom-doped C2N monolayers and the first-step reaction mechanism of CO2RR were investigated by density functional theory (DFT). The catalyst structure, CO2 adsorption configuration and electronic properties of CO2 activation on C2N surfaces decorated with transition metal single atoms of Cu, Co, and Ni were discussed. Cu/C2N, Co/C2N and Ni/C2N all have good CO2 adsorption performance by calculations. The calculation results of the first hydrogenation reaction of CO2RR show that the three materials of Cu/C2N, Co/C2N and Ni/C2N have lower energy barriers than the pristine C2N, which suggests that they are more favorable for the CO2RR reaction to proceed. The Cu/C2N surface is more inclined to adsorb CO2 and then combine with H atoms to form OCHO, but the Co/C2N and Ni/C2N surfaces are more inclined to hydrogenate CO2 to COOH in one step. The difference in the mechanism of the three material systems may be due to the difference of electrons and density of states on the 4s orbital of the outermost electron number of the doped transition metal atoms Cu, Co, Ni.